1. Related Applications
This application claims priority under 35 USC 119 from GB 9008424.5 filed Apr. 12, 1990.
2. Field of the Invention
The present invention relates to power take-off (PTO) engagement mechanism by which a driven PTO shaft can be engaged or disengaged with a rotating input shaft communicating with a power source, e.g. a driving shaft of a heavy duty vehicle change gear transmission. Since PTO's often transmit large amounts of power, e.g. at temporary sites for operating or winching large and/or heavy duty equipment, the required parts, splines, etc., of the engagement mechanism must be robust and accordingly often use pressurized fluid such as pneumatic power to actuate the toothed clutching members that engage and disengage the PTO.
More particularly, the present invention relates to a pressurized fluid actuated PTO engagement mechanism of the type comprising a driving input shaft, a coaxial driving gear independently rotatable of said input shaft and selectively axially movable into and out of engagement therewith and a driven gear constantly meshing with said driving gear and in driving relationship with the PTO output shaft.
3. Description of the Prior Art
Selectively engageable and disengageable PTO devices driven off heavy duty (i.e. truck) vehicular transmissions are, of course, well known in the prior art as may be seen by reference to U.S. Pat. Nos. 4,388,843; 3,830,111; 2,958,225; 2,761,322 and 2,438,539, the disclosures of which are hereby incorporated by reference.
One prior art PTO engagement mechanism involves an axially fixed shaft rotating with and within a bore in the PTO input gear, the shaft having a longitudinal conduit to conduct pressured fluid to an operating chamber, and a piston axially driven by the pressure at the chamber and taking the gear with it against a disengaging bias to a position of engagement with the rotating input shaft.
Accordingly, the state of the art is a PTO engagement mechanism comprising a housing, a PTO input gear mounted therein with sliding and rotational freedom, a piston fixed to the gear and drivable axially by a pressure chamber formed at the end of a center drilled shaft until a meshing part of the gear (i.e. a first jaw clutch member) meshes with a cooperatingly meshing part (i.e. a second jaw clutch member) of an input shaft. The center drilled shaft passes through a central bore in the gear, a conduit in the shaft is proved to introduce and vent pressurized air to and from the pressure chamber and a return bias is proved acting to resist engaging movement of the gear.
The above-described prior art arrangement, described in greater detail hereinafter, uses many parts, seals, 0-rings, bearings. It is desirable to provide an improved mechanism which will, compared to the prior art, reduce the number of parts, weight, length (always at a premium in mobile machinery) and/or of leak paths of high pressure fluid or oil.